Boat



R. P. SWANSON 3,195,154

July 20, 1965 BOAT 2 Sheets-Sheet 1 Filed March 9, 1964 mm S mm WW 9 R E G O R M4 Jazz-2%, 2%;

ATTDBN EYS July 20, 1965 R. P. SWANSON BOAT 2 Sheets-Sheet 2 Filed March 9. 1964 FIGS INVENTOR.

ROGER E SWANSON ATTORNEY:

United States Patent BOAT Roger P. Swanson, Lexington, Mass, assignor to Alumahrt Company, Inc, Salem, Mass, a corporation of Massachusetts Filed Mar. 9, 1964, Ser. No. 350,261 Claims. (Cl. 96)

This invention relates to a boat construction and more particularly to a boat having inner and outer sheet aluminum hulls between which a rigid plastic core layer is foamed in place.

Light-weight aluminum boats are well-known in the industry. For example, my previous U.S. Patent No. 3,064,283, discloses a metal boat having a single hull. Furthermore, double hulled boats have been known, chiefly made from fiberglass materials.

However, the novel construction of the preferred embodiment of this invention combines a double hull, made of aluminum sheet metal, with an expanded rigid urethane foam filler which is foamed in place within the hull walls to produce an extremely rigid hull structure which takes advantage of the strength and low maintenance characteristics of aluminum while taking further advantage of the flotation and sound dampening characteristics of urethane foam.

Accordingly, it is an object of this invention to provide a boat construction which has a double hull giving substantial protection against through-hull holes and punctures.

It is a further object of this invention to provide a boat construction having a double hull with a foamed plastic filler therebetween which dampens the motor-produced sonic vibrations as well as the pounding caused by the waves.

It is a further object of this invention to provide a boat construction having a double hull with a foamed plastic filler therebetween which provides sufiicient flotation to keep the boat afloat even when the boat is swamped or has large holes in the hull.

It is a further object of this invention to provide a boat construction having a double hull and a foamed plastic filler therebetween which has great structural strength and rigidity and which provides a hull floor which has a solid feel when walked upon.

It is a further object of this invention to provide a boat construction having a double hull made from aluminum sheeting which is light-Weight, has a low cost, is virtually maintenance-free, requires no painting, is easy to patch if holed and resists deterioration because of the weatherproof materials employed in its construction.

It is a further object of this invention to provide a boat construction having a double aluminum hull with a foamed plastic filler therebetween which utilizes the benefits of aluminum yet does not generate the noise characteristic commonly associated with aluminum boat construction.

It is a still further object of this invention to provide a boat construction having a double hull with a foamed plastic filler therebetween which construction further has a specially designed gunwale strip spanning the upstanding free edges of the bulls which is fastened only to the outer hull and is maintained in engagement with the inner hull solely by the pressure exerted by the foamed plastic filler against the nested hulls. This arrangement obviates the need for through-hull fittings.

The invention will be more fully set forth in the following description and accompanying drawings, and the features of novelty will be pointed out with particularity in the claims annexed to and forming a part of this specification.

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Referring to the drawings:

FIG. 1 is a view in perspective of the boat incorporating the invention;

FIG. 2 is a plan view of an aluminum sheet from which the outer hull is fabricated. The sheet has been cut to shape but not yet bent;

FIG. 3 is a plan view of an aluminum sheet from which the inner hull is fabricated;

FIG. 4 is a view in perspective, partly broken away, of the boat showing the inner and outer hulls and the rigid plastic foam layer therebetween; and

FIG. 5 is a view in front elevation, partly broken away, showing in detail the gunwale member in engagement with the inner and outer hulls.

Referring now more particularly to the drawings, the boat, illustrated in FIG. 1, has a hull, generally designated as it}, which forms a pointed bow 12 and a squared-oft stern or transom 14. Three seat members 16 are fastened to the side walls of the hull. Accessories, such as corner sections 18, lifting handles 26 and outboard motor 22 complete the superficial description of the small open boat of the preferred embodiment of this invention.

Looking now at FIG. 2 and having particular reference to my previous U.S. Patent No. 3,064,283, it will be understood that a light-weight substantially rigid aluminum sheet is cut or blanked as shown to form a bottom section 24, side sections 26 and 28 and a transom section 30. Two longitudinal keels 31 and 33 are formed in the bottom section 24 adjacent the centerline. The aluminum sheet is cut in such a way that three bending operations will form the bow portion of the hull. First, the side walls 26 and 28 are bent up from the bottom 24 along the dotted bend lines. Second, the forward portions of the side Walls 26 and 28 are bent in a converging curve until the bow edges 40 and 42 meet. Third, the bottom section 24 is bent up until its curved edges 36 and 38 meet the lower side wall edges 32 and 34. All the meeting edges are joined, preferably by welding. It will be noticed that the tapered forward portions of side walls 26 and 28 require the hull bottom 24 to rise slightly at the bow which is a desirable feature contributing to the superior handling characteristics of the boat in the water.

The formation of the transom portion of the hull is accomplished by two bending operations. First, the transom section 30 is bent up from the bottom 24 along the dotted bend line until it is substantially vertical. Second, corner sections 44 and 46, having substantially the form of a right triangle, are bent in perpendicular to the side walls 26 and 23 along the dotted corner bend lines. The corner sections 44 and 46 are then lying in the vertical plane defined by the transom section 30. The edges 48 and 50 of corner sections 44 and 46 are thus adjacent to and abut the edges 52 and 54 of transom section 30 and are welded thereto. It is to be noted that these welds are perpendicular to the bottom 24 and are spacedinboard of the stern corners of the boat so as to increase the structural strength of the stern.

The forming of the outer boat hull 56 as just described is generally set out in my previously mentioned patent.

Looking now to FIG. 3, it will be seen that the inner boat hull 58 is essentially identical with outer boat hull 56 except that it is of slightly smaller dimensions and the sheet is optionally cut out with the stern corner sections 60 and 62 formed integral with the transom section whereby the transom-side wall welds are made at the right-angled stern corners instead of being butt-welded in the plane of the transom, as was done in fabricating the outer hull 56. It is to be understood that inner hull 58 could also be made in the exact same manner as outer hull ss. Two small holes 60 and 62 are drilled or punched in bottom section 24 for a purpose to be subsequently explained.

It will now be seen that inner hull 58 is dimensioned and shaped to nest within outer hull 56. Preferably, inner hull 58 is made from lighter weight aluminum (e.g. .032 inch) whereas outer hull 56 is made from heavier weight aluminum'(e.g. .040 inch). l V

The facing portions of the inner and outer hulls,i.e. the upper surface of outer hull 56 and the lower surface of inner hull 58, are detergent cleaned or steam cleaned. These facing portions are then spray painted with a wash primer suchas a zinc chromate primer.

A longitudinal bracing member 64, shown most clearly in FIG. 4, having an I-beam shape and extending from the bow to the stern, is cemented, or otherwise attached, to the upper surface of outer hull 56. Inner hull 53 is nested or placed within outer hull 58 and rests upon longitudinal bracing member 64. The nested hulls are then placed in an underlying female mold, not shown, which is shaped to provide-complete support to outer hull 56. The female mold has aconcrete and plywood construction within which is embedded a network of copper tubing through which warm water is circulated to maintain the female mold at a temperature preferably in the range of 90- A specially designed channel-shaped gunwale member "66, shown in detail in FIG; 5, is applied over the free upstanding edges of the inner and outer nested hulls. Gunwale member on has an upper horizontal body porouter hulls. Depending from the lower surface of horizontal body portion 68 is a bifurcated channel wall 72 whichhas a pair of forked fingers 74 and 76 spaced apart a distanceequal to the skin thickness of outer hull 56. Fasteners 78, preferably blind rivets, are driven through and securely fasten. fingers 74 and 76 to the upstanding free edge of outer hull 56 which is inserted between the fingers. The rivets are spaced about every twelve inches along the gunwale. Depending from the inner edge of horizontal body portion 63 is an inner channel wall 70 spaced from the bifurcated channel wall 72. Inner wall 76 supportably abuts, but is not fastened to, the upstand- "ing free edge of inner hull 58. It will now be seen that 'channel walls 70 and 72 embrace the free edges of inner and outer hulls 56 and 53. Hull 56 is fastened to the gunwale and hull 58 is confined by it and prevented from inward movement.

Depending from the outer edge of horizontal body portion 68 is rub rail 80 which is curled in at its lower extremity. The rub rail extends outboard of the double hull structure and the other portions of the gunwale member 66. The rub rail is designed to partially protect the boat hull from damage which might otherwise be caused by contact with the dock or other boats. Of course, the rail does; not eliminate the need for fenders. covering could easilybe applied over the surface of the rub rail 80 and the upper horizontal body portion 68 and could be anchored to inner channel Wall 70. i

A male plug (not shown) shaped to conform to the tion 68 extending across the gap between the inner and.

A vinyl inner dimensions of inner hull 58 is placed therein and held in position by conventional hold-down means. The male plug has two recesses permitting access to inner hull holes and 62. It will thus be seen that the female mold and the male plug securely anchor and immobilize the nested spaced apart boat hulls between which a cavity has been created. Furthermore, the outer hull 56 is maintained at a temperature of approximately 90100 F. by the heated female mold through which hot water circulates. V p r The between-hull cavity is preferably filled with rigid .closed cell urethane foam which is foamed in ,place by known frothing techniques, an example of which will be subsequently described. This urethane foam core layer 32 bonds to and exerts pressure against the hull walls and bottomwhich forces inner hull 58 tightly against the inner channel wall 70 and the upper horizontal body portion 68 of gunwale 66. This joinder arrangement pro- 100 F. and 100% relative humidity:

vides the inner channel wall with a perfectly smooth inner surface in which there are no rivets or screws to work loose or to scratch and snag the boat occupants. Also, this eliminates through-hull fittings which often cause leaking. Furthermore labor .costs to fasten the inner hull to the gunwale are eliminated.

In the preferred'embodiment, it has been found that urethane foam having the following properties is satisfactory for the core layer 82. The property values were determined from tests made on a panel 8' x 4' x 4 frothed in a vertical position. The values are given for purposes of example only.

Density 1.9 lb./cu. ft.

Compressive yield strength 30 psi. (yield point Closed cell content v at 7% deflection).

91% (uncorrected for cut surface).

Dimensional stability (percent maximum linear change) (4" x 4" x 3%" testing samples) Percent 1 day 1.7 7days 2.1

158 F. and 100% relative humidity: 1 day 7.2 7 days u, 10.3

The urethane foam that is injectedintothe betweenhull cavity is produced in the preferred embodiment by a ,frothing process utilizing a prepolymer component and a blowing agent component which are mixed and delivered as partially expanded foam at 5 to 15 lb./min. having a density'of 3 to 10 lb./ cu. ft." The prepolymer component consists of isocyanate, such as t-olylene diisocyanate, ether glycol resin and an emulsifier. The blowing agent component consists of ether glycol resin, a catalyst and a propellant such as dichlorodifiuoromethane (CCl F as for example Freon- 12 manufactured by E. I. du 'Pont de Nemours & Co., Wilmington, Delaware,

' The two components are stored separately and brought together immediatelyprior to the filling of the cavity. The

components are mixed and the foaming'resultant composition is delivered into the cavity through holes '60 and '60 and 62 should be plugged and the boat removed to a curing room for at least an eight hour period duringwhich the temperature should be maintained at 8090" F.

Having now described, in detail, the construction of my preferred embodiment, it will be appreciated that I have provided a boat which secures the maximum advantages from the use of sheet aluminumas the hull material and closed cell rigid urethane foam as the core material. The

. boat has, as a unique feature, a gunwale strip which is fastened only to the outer hull and thereby presents a smooth surface to the boat occupants. No through-hull fittings are needed and fabrication costs are reduced through use of this gunwale. The construction process is simple, inexpensive and can be accomplished without expensive dies and heavy machinery.

Obviously, many modifications and variations of the present invention are possible in light of the above teachlngs Therefore, it is to be understood that the invention is not to be limited to the details of the construction and arrangement of parts specifically described or illus trated, but is to be limited only by the spirit of the invention and the scope of the annexed claims.

I claim:

1. A boat comprising: a sheet metal outer hull; a sheet metal inner hull constructed and dimensioned to nest within said outer hull; means positioned between said hulls for spacing said outer hull from said inner hull forming a cavity therebetween; a gunwale member embracing the upstanding spaced apart free edges of said outer and inner hulls and spanning the distance therebetween, said gunwale member positively maintaining the free edges of said hulls at a fixed spacing therebetween, said gunwale member having a horizontal body portion formed with an inner downwardly depending channel Wall for supportably contacting the upstanding free edge of said inner hull, said gunwale body portion further being formed with a central downwardly depending bifurcated channel wall for slitting over and being fastened to the upstanding free edge of said outer hull, said body portion further being for-med with an outer downwardly depending and inwardly turned rub rail portion, the outermost vertical surface of which extends outboard of said outer hull contour; and a layer of foamed plastic completely filling said between-hull cavity.

2.. The boat of claim 1 wherein said means for spacing said outer hull from said inner h-ull includes a longitudin-al member extending from the bow to the stern, said member being affixed to at least one of said hulls.

3. The boat of claim 2 wherein said longitudinal member has an I-beam cross section.

4-. The boat of claim 1 wherein said layer of foamed plastic is rigid and foamed in place.

'5. The boat of claim 1 wherein said layer of foamed plastic is closed cell urethane.

6. A boat comprising: a sheet aluminum outer hull; a sheet aluminum inner hull fabricated and dimensioned to nest within said outer hull; a longitudinal spacing member positioned between said nested hulls and afiixed to said outer bull to form an interior cavity between the hulls, said longitudinal member extending from the bow to the stern and further acting to resist bending forces applied to the outer hull bottom; a gunwale member extending around the upstanding spaced apart free edges of said outer and inner hulls and spanning the distance therebetween, said gunwale member having a horizontal upper body portion and three integrally formed downwardly depending vertical portions including an inner lip for supportably abutting the free upstanding edge and the inner surface of said inner hull, a central bifurcated lip for fitting over and being fastened to the upstanding free edge of said outer hull, and an outer rub rail portion that is turned in at its lower edge; and a layer of foamed rigid urethane plastic completely filling the interior cavity between the bulls.

7. A boat comprising: a sheet metal outer hull; .a sheet metal inner hull constructed and dimensioned to nest within said outer hull; means positioned between said hulls for spacing said outer hull from said inner hull forming a cavity therebetween; a gunwale member embracing the upstanding spaced apart free edges of said inner and outer nested hulls, said gunwale member having a horizontal wall spanning said hulls and extending outboard of said outer hull, said horizontal wall having an integral downturned and interned rub rail formed at the outboard margin thereof, said gunwale member further having two depending flanges, one of said flanges being imperforate and abutting the inner surface of said inner hull, the other of said flanges abutting the outer surface of said outer hull and being secured thereto; and a layer of foamed plastic completely filling said between-hull cavity.

8. Apparatus of claim 7 wherein the other of said flanges is bifurcated at its lower end to additionally abut the inner surface of said outer hull.

'9. A boat comprising: a sheet metal outer hull; a sheet metal inner hull constructed and dimensioned to nest within said outer hull; means positioned between said hulls for spacing said outer hull from said inner hull forming a cavity therebetween; a gunwale member applied over the upstanding free edges of said inner and outer nested hulls, said gunwale member having a horizontal wall spanning said hulls and two integral depending flanges, one of said flanges being imperforate and abutting the inner surface of said inner hull, the other of said flanges being bifurcated at its lower end and abutting both surfaces of said outer hull and vfastened thereto, said horizontal wall extending outboard of said outer hull and having a rub rail formed at the outboard margin thereof; and a layer of foamed rigid urethane plastic completely filling the between-hull cavity.

10. In a boat construction of the type having a sheet metal outer hull, a sheet metal inner hull dimensioned to nest within said outer hull, means positioned between said hulls for spacing said hulls apart forming a cavity therebetween, and a layer of foamed plastic completely til-ling said between-hull cavity, the improvement therein comprising: a gunwale member applied over the upstanding spaced apart free edges of said nested hulls, said gunwale member having a horizontal wall spanning said hulls and two integral depending flanges, one of said flanges being imperforate and abutting the inner surface of said inner hull, the other of said flanges being bifurcated at its lower end and abutting both surfaces of said outer hull and fastened thereto, said horizontal wail extending out-board of said outer hull and being downturned and inturned to form a rub rail.

References (Iited by the Examiner UNITED STATES PATENTS 2,855,885 10/58 Thomas 9--6 13,007,208 11/61 Urban 9-6 3,007,224 1-1/61 Wean.

3,013,922 12/61 Fisher 96 X 3,032,785 5/62 Ward et a1 96 3,065,724 1 1/62 Tritt 114-88 3,126,557 3/64- Stevens 96 MILTON BUCHLER, Primary Examiner.

FERGUS S. MIDDLETON, Examiner. 

1. A BOAT COMPRISING: A SHEET METAL OUTER HULL; A SHEET METAL INNER HULL CONSTRUCTED AND DIMENSIONED TO NEST WITHIN SAID OUTER HULL; MEANS POSITIONED BETWEEN SAID HULLS FOR SPACING SAID OUTER HULL FROM SAID INNER HULL FORMING A CAVITY THEREBETWEEN; A GUNWALE MEMBER EMBRACING THE UPSTANDING SPACED APART FREE EDGES OF SAID OUTER AND INNER HULLS AND SPANNING THE DISTANCE THEREBETWEEN, SAID GUNWALE MEMBER POSITIVELY MAINTAINING THE FREE EDGES OF SAID HULLS AT A FIXED SPACING THEREBETWEEN, SAID GUNWALE MEMBER HAVING A HORIZONTAL BODY PORTION FORMED WITH AN INNER DOWNWARDLY DEPENDING CHANNEL WALL FOR SUPPORTABLY CONTACTING THE UPSTANDING FREE EDGE OF SAID INNER HULL, SAID GUNWALE BODY PORTION FURTHER BEING FORMED WITH A CENTRAL DOWNWARDLY DEPENDING BIFURCATED CHANNEL WALL FOR FITTING OVER AND BEING FASTENED TO THE UPSTANDING FREE EDGE OF SAID OUTER HULL, SAID BODY PORTION FURTHER BEING FORMED WITH AN OUTER DOWNWARDLY DEPENDING AND INWARDLY TURNED RUB RAIL PORTION, THE OUTERMOST VERTICAL SURFACE OF WHICH EXTENDS OUTBOARD OF SAID OUTER HULL CONTOUR; AND A LAYER OF FOAMED PLASTIC COMPLETELY FILLING SAID BETWEEN-HULL CAVITY. 